Lapping machine



March 26, 1968 S. A. BOETTCHER LAPPING MACHINE Filed Dec. 8, 1964 United States Patent G 3,374,582 LAPPING MACHINE Stephen A. Boettcher, Deer-field, Ill., assignor to Speedfam Corporation, a corporation of Illinois Filed Dec. 8, 1964, Ser. No. 416,825 14 Claims. (Cl. 51-131) ABTRAT OF THE BHSCLGSURE A contour control member positionable with the lower annular surface thereof in engagement with the outer portion of the periphery of a lapping disc between adjacent truing and retaining rings for dressing the lapping surface of the disc.

generally to lapping maapparatus for controlling My present invention relates chines and more particularly to the contour of lapping surfaces.

The general type of lapping machine with which the principles of my present invention may be incorporated includes a lapping disc rotatably driven about a vertical axis. Resting on the horizontal annular lapping surface of the lapping disc are retaining and truing rings which are normally rotatable about their own axes freely by frictional contact with the lapping surface. These rings are provided for holding pieces within them against movement with the rotating lapping disc, and for wearing the lapping surface to tend to keep it planar. However, even with the provision of the described truing rings, more wear of the lapping surface occurs in the inner annular portion than in the outer annular portion. In a lapping machine of this type, the necessary planar condition of the annular lapping surface of the lapping disc may be restored by driving the rings in reverse of normal direction. But this procedure is disadvantageous because it requires special drive means between the lapping disc and the rings, and, in some cases, also requires special rings.

It is an object of my present invention to provide app.- ratus for use in a lapping machine for selectively dressing the outer annular portion of the lapping surface of the lapping disc.

It is another object of my present invention to provide apparatus for use in a lapping machine for complementing the tiuing rings in controlling the contour of the lapping surface of the lapping disc.

It is another object of my present invention to provide apparatus, as described, for controlling the contour of the lapping surface of a lapping disc without interrupting the normal operation of the lapping machine.

In the accomplishment of these objects, I provide at least one contour control member having a diameter substantially less than the diameter of each of the truing and retaining rings and having a lower surface engageable with the lapping surface. Suitable means are secured to the framework of the lapping machine for rotatably mounting the contour control member about a vertical axis and for positioning the contour control member adjacent the outer periphery of the lapping disc circumferentially intermediate of two of the truing rings. The means for rotatably mounting the contour control member includes power means for raising and lowering the contour control member and for selectively urging the latter into frictional engagement with the lapping disc. To correct the contour of the lapping surface, the contour control member is urged into engagement with the lapping surface under a constant pressure at intervals and for varyingperiods of time, as may be necessary, to dress the lapping surface adjacent the outer periphery thereof. Thus, the contour control member serves to wear the lapping surface in the outer annular portion therof whereby to quickly and controllably restore the lapping surface to a planar condi- 3,374,582 Patented Mar. 26, 1968 tion. Alternatively, to accommodate variations in the rate of wear of different portions of the lapping surface of the lapping disc, the contour control member could be urged into engagement with the lapping surface under a continuous but variable pressure.

It is a further object of my present invention to provide apparatus for controlling the contour of the lapping surface of a lapping disc, as described, wherein the contour control member includes an annular wear ring secured within a holder.

Now in order to acquaint those skilled in the art with the manner of constructing and using apparatus in accordance with the principles of my present invention, I shall describe in connection with the accompanying drawing a preferred embodiment of my invention.

In the drawing:

FIGURE 1 is a perspective view of a typical lapping machine with which the apparatus of my present invention has been incorporated;

FIGURE 2 is an enlarged view, partly in section and partly in elevation, of the contour control device of my present invention;

FIGURE 3 is a bottom view of the contour control device of FIGURE 2; and

FIGURE 4 is a schematic plan view of the geometrical arrangement of tie truing rings and the contour control members relative to the lapping disc of the lapping machine of FIGURE 1.

Referring now to FIGURE 1, there is indicated generally by the reference numeral 10 a typical lapping machine with which the apparatus of my present invention may be incorporated. The lapping machine ill comprises a framework including a tubular base or housing 12 which provides support for a horizontal lapping disc 14 and a staging table 16 surrounding the lapping disc. The lapping disc 14 is formed with a central recess 17 (FIG- URE 4) whereby to define a horizontal annular lapping surface. Selective rotation of the lapping disc 14 about a vertical axis is effected by drive means (not shown) mounted Within the housing 12. Suitably secured to the opposite sides of the housing 12 are the lower ends of vertical columns 18. Extending between the upper ends of the columns 18, above the lapping disc 14, is a horizontal bridge member 29 provided with transverse arms 22 which number four in the particular lapping machine herein disclosed. Mounted at the outer ends of each of the transverse arms 22 is a vertical pneumatic piston and cylinder assembly indicated generally by the reference numeral 24. Each of the pneumatic assemblies 24 includes a cylinder 26 and a piston rod 23. The lower ends of the piston rods 28 are secured to horizontal pressure plates (not shown) which fit, with slight clearance, within truing and retaining rings 3% resting on the horizontal lapping surface of the lapping disc 14. As shown in FIG- URE 4, the rings 30 slightly overlap the inner and outer peripheries of the annular lapping surface. When the lapping disc 14 is rotated, the truing rings 33 rotate relative to the pressure plates about the axes defined by the piston rods 28 whereby to serve to dress the lapping surface of the lapping disc 14 for substantial maintenance of its planar condition. Work pieces (not shown) to be lapped are adapted to be confined Within the truing rings 30 below the pressure plates therein. During the lapping operation, a freely flowing mixture of abrasive particles and an oil carrier is fed to the lapping disc 14 in a known manner.

Experience has shown that, even with the provision of the truing and retaining rings 3%), the inner annular portion of the lapping surface of the lapping disc 14- wears m-ore rapidly than the outer annular portion. According- 1y, heretofore it has been necessary to periodically drive the rings 30 in reverse of normal direction to restore the 3 lapping surfaceto a planar condition. Such procedure requires special drive means between the lapping disc and the rings, and may, in addition, require special rings. To obviate these requirements, I provide at least one, and preferably two, contour control devices indicated generally by the reference numeral 32.

'Each contour control device 32 includes a supporting bracket 34 extending laterally from the column 18 in the direction of the lapping disc 14. As best shown in FIG- URES 2 and 3, the bracket 34 has suitably secured thereto the lower end of the cylinder 36 of a vertically extending pneumatic piston and cylinder assembly 38. The piston rod 40 of the pneumatic assembly 38 projects downwardly through the bracket 34, and threaded into the lower end of the piston rod 40 is a bolt 42. Secured in assembled position between the end of the piston rod 40 and the head of the bolt 42 are an inverted cup-shaped casing 44, a bushing 46, and a split collar member 48 having a lower conical face. Engagement of the head of the bolt 42 with the conical face of the collar member 48 serves to expand the latter into tight contact with the inner race of a self-aligning ball thrust bearing assembly 50. The outer annular aligning sleeve of the bearing assembly St is received in an annular recess defined by an annular clamp ring 52 and an annular spacer member 54. Extending through the ring 52 and spacer 54 are a plurality of circumferentially spaced bolts 56 which, at their lower ends, are threaded into openings formed in a disc-like holder 58. Formed in the lower face of the holder 58 are a central circular recess 60 and a concentric annular recess 62 in which is secured, as by epoxy cement or the like, an annular wear ring 64. The wear ring 64 must be fabricated of a material having a greater abrasion resistance than the material of the lapping disc 14 and is preferably of a high wear resistant material such as boron carbide. A central axial opening 66 is also formed in the holder 58 to permit insertion therethrough of an instrument such as a screw driver whereby threading and unthreading of the screw 42 relative to the piston rod 40 may be effected. The holder 58 and wear ring 64 define a contour control member 68.

As shown in FIGURE 4, each contour control member 68 has a maximum horizontal dimension or diameter substantially less than the radial distance between the inner and outer peripheries of the lapping surface of the lapping disc 14, and substantially less than the diameter of each of the retaining rings 30.'Also, the radial distance between the axis of rotation of the lapping disc 14 and the axis of rotation of each of the contour control members 68 is greater than the radial distance between the axis of rotation of the lapping disc 14 and the axis of rotation of each of the truing rings 30. The power operated pneumatic piston and cylinder assemblies 38, which are supported by the brackets 34, are operable to raise and lower the contour control members 68 and to selectively urge the annular lower surfaces of the latter into frictional engagement with the lapping surface of the lapping disc 14 circumferentially intermediate of the adjacent truing and retaining rings 30. The ball bearing assembly 50 and related structure of each device 32 serve to rotatably mount the contour control member 68 about a vertical axis. Thus, when the contour control members 68 are urged into frictional contact with the lapping surface of the lapping disc 14, they rotate on their own axes. Still further, the pneumatic assemblies 38 and supporting brackets 34 serve to position the contour control members 68 adjacent to the outer periphery of the lapping disc 14 and in slightly overlapping relation with respect to the outer periphery thereof.

When corrective treatment of the lapping surface of the lapping disc 14 is necessary, the pneumatic assemblies 38 are actuated so as to lower the contour control members 68 and thereby urge the wear rings 60 under pressure into frictional engagement with the lapping surface. I have found that a constant contact pressure of pounds per square inch is satisfactory. When the correctivetreatment has been completed and the contour of the lapping surface of the lapping disc 14 restored to a planar condition, the pneumatic assemblies 38 are actuated so as to raise the contour control members 68 away from the lapping disc 14. The contour control members 68 are maintained in an elevated position until such time as corrective treatment of the lapping surface is again necessary. The apparatus of my present invention is adapted to be used at intervals and for varying periods of time, as may be necessary, to dress the outer annular portion of the lapping surface of the lapping' disc 14. Thus, this apparatus, which may be used without interrupting the normal operation of the lapping machine, serves to complement the truing rings in controlling the contour of the lapping surface of the lapping disc 14. Finally, by arranging the contour control devices 32 at the sides of the lapping machine, interference with loading and unloading of the machine is avoided.

While I have shown and described what I believe to be a preferred embodiment of my present invention, it will be understood by those skilled in the art that various rearrangements and modifications may be made therein without departing from the spirit and scope of my invention.

I claim:

1. For use in a lapping machine having a framework and a lapping disc with an annular lapping surface rotatably mounted about a vertical axis on the framework, the combination of a contour control member having a diameter substantially less than the radial distance between the inner and outer peripheries of the lapping surface and having an annular lower horizontal surface selectively engageable with the lapping surface, and means secured to the framework for positioning said contour control member adjacent the outer periphery of the lapping surface. 7

2. For use in a lapping machine having a framework and a lapping disc with an annular lapping surface rotatably mounted about a vertical axis on the framework, the combination of a contour control member having a diameter substantially less than the radius of the lapping disc and having a lower annular surface engageable exclusively with the outer annular zone of the lapping surface, and power means secured to the framework for selectively urging said contour control member under pressure into frictional engagement with the lapping surface.

3. For use in a lapping machine having a framework and a lapping disc with an annular lapping surface rotatably mounted about a vertical axis on the framework, the combination of a contour control member having a diameter substantially less than the radial distance between the inner and outer peripheries of the lapping surface and having an annular surface e'ngageable with the lapping surface, means secured to the framework for rotatably mounting said contour control member about a vertical axis and for positioning the latter so as to slightly overlap the outer periphery, of the lapping surface and said lastnamed means including. power means for raising and lowering said contour control member and for selectively urging the latter under pressure into frictional engagement with the lapping surface.

4. For use in a lapping machine having a framework and a lapping disc with an annular lapping surface rotatably mounted about a vertical axis on the framework, the combination of a contour control member having an annular wear ring secured within a holder, the overall diameter of said contour control member being substantially less than the radial distance between the inner and outer peripheries of the lapping surface, and means secured to the framework for rotatably mounting said contour control member about a vertical axis and for selectively positioning said wear ring in engagement with the outer annular zone of the lapping surface.

5. The combination of claim 4 wherein said wear ring is comprised of a material having a greater abrasion resistance than the material of the lapping disc.

6. For use with a lapping machine having a framework, a lapping disc rotatably mounted about a vertical axis on the framework, means for rotating the lapping disc, the lapping disc having a horizontal planar lapping surface, and retaining and truing rings resting on the lapping surface, the combination of a contour control member having a maximum horizontal dimension substantially less than the diameter of each of the retaining rings and having a lower horizontal surface selectively engageable with the lapping surface, and means secured to the framework for positioning said contour control member circumferentially intermediate of two of the retaining rings.

7. For use with a lapping machine having a framework, a lapping disc rotatably mounted about a vertical axis on the framework, means for rotating the lapping disc, the lapping disc having a horizontal planar lapping surface, and retaining and truing rings resting on the lapping surface, the combination of a contour control member having a diameter substantially less than the diameter of each of the retaining rings and having a lower horizontal surface selectively engageable with the lapping surface, and means secured to the framework for positioning said contour control member adjacent the outer periphery of the lapping disc circumferentially intermediate of two retaining rings.

8. For use with a lapping machine having a framework, a lapping disc rotatably mounted about a vertical axis on the framework, means for rotating the lapping disc, the lapping disc having a horizontal planar lapping surface, and retaining and truing rings resting on the lapping surface, the combination of a contour control member having a diameter substantially less than the diameter of each of the retaining rings and having an annular lower horizontal surface selectively engageable with the lapping surface, and means secured to the framework for positioning said contour control member so as to slightly overlap the outer periphery of the lapping disc circumferentially intermediate of two of the retaining rings.

9. For use with a lapping machine having a framework, a lapping disc rotatably mounted about a vertical axis on the framework, means for rotating the lapping disc, the lapping disc having a horizontal planar lapping surface, and retaining and truing rings resting on the lapping surface and normally rotatable about their own axes, the combination of a contour control member having a lower surface engageable with the lapping surface, and means secured to the framework for rotatably mounting said contour control member about a vertical axis, with the radial distance between the axis of rotation of the lapping disc and the axis of rotation of said contour control member being greater than the radial distance between the axis of rotation of the lapping disc and each of the axes of rotation of the retaining rings.

10. For use with a lapping machine having a framework, a lapping disc rotatably mounted about a vertical axis on the framework, means for rotating the lapping disc, the lapping disc having a horizontal planar lapping surface, and retaining and truing rings resting on the lapping surface, the combination of a contour control member having an annular wear ring secured within a holder, the overall diameter of said contour control memher being substantially less than the diameter of each of the retaining rings, and means secured to the framework for rotatably mounting said contour control memher about a vertical axis and for selectively positioning said wear ring in engagement with the lapping disc.

11. The combination of claim 10 wherein said wear ring is comprised of a material having a greater abrasion resistance than the material of the lapping disc.

12. For use with a lapping machine having a framework, a lapping disc rotatably mounted about :a vertical axis on the framework, means for rotating the lapping disc, the lapping disc having a horizontal planar lapping surface, and retaining and truing rings resting on the lapping surface, the combination of a contour control member having a diameter substantially less than the diameter of each of the retaining rings and having a lower horizontal surface engageable with the lapping surface, means secured to the framework for positioning said contour control member adjacent the outer periphery of the lapping disc circumferentially intermediate of two of the retaining rings, and said last-named means including power means for selectively urging said contour control member under pressure into frictional engagement with the lapping surface.

13. For use with a lapping machine having a framework, a lapping disc rotatably mounted about a vertical axis on the framework, means for rotating the lapping disc, the lapping disc having a horizontal planar lapping surface, and retaining and truing rings resting on the lapping surface and normally rotatable about their own axes, the combination of a contour control member having an annular wear ring secured within a holder, the overall diameter of said contour control member being substantially less than the diameter of each of the retaining rings, means secured to the framework for rotatably mounting said contour control member about a vertical axis and for positioning said contour control member adjacent the outer periphery of the lapping disc circumferentially intermediate of two of the retaining rings, With the radial distance between the axis of rotation of the lapping disc and the axis of rotation of said contour control member being greater than the radial distance between the axis of rotation of the lapping disc and each of the axes of rotation of the retaining rings, and said last-named means including power means for raising and lowering said contour control member and for selectively urging said wear ring under pressure into frictional engagement with the lapping surface.

14. The combination of claim 13 wherein said wear ring is comprised of boron carbide.

References Cited UNITED STATES PATENTS 2,079,076 5/ 1934 Kranich 51-131 2,687,603 8/1954 White 51-131 2,968,135 1/1961 Boettcher 51-129 2,979,868 4/1961 Emeis 51-131 FOREIGN PATENTS 913,570 6/ 1946 France. 1,093,251 11/ 1960 Germany.

HAROLD D. WHITEHEAD, Primary Examiner. 

